Such a method and such a device have previously been described in DE 39 15 812 A1. DE 39, 15 812 A1 describes concentrically disposed coils or a cylindrically formed capacitor for power transmission. A signal transmission may likewise occur by means of the coils or the capacitor or via radio.
The disadvantage here is that during the transmission of signals by means of this same assembly, which is also used for the power transmission, a mutual influence on the transmission cannot be excluded. An optimized power transmission also regularly requires a different design adaptation of the coils and the capacitor as an optimized signal transmission so that the use of this very same assembly of transmitters can only ever be a less than optimal compromise.
If the signal is transmitted via radio, the device for power transmission may in principle indeed be optimally designed for this purpose. Radio transmission is, however, frequently susceptible to external interference and can be influenced with appropriate means by way of external transmitters, which is particularly disadvantageous with regard to security-related signals.